ByScott Smith, Associated PressSeptember 5, 2015

In this Aug. 21, 2015 photo, a firefighting crew member, background, stands beyond a firing operation burning the understory fuel along Highway 180 just north of the Hume Lake turnoff in the Sequoia National Forest. California’s largest wildfire burning near the popular Hume Lake in the Central Sierra Nevada is expected to rage through the holiday weekend, and the forestry officials encourage campers to set up their tents elsewhere.

FRESNO, Calif. — A vast and stubborn wildfire that has proven California's biggest this year was expect to spew smoke through the long Labor Day weekend, leaving some campgrounds empty and prompting health warnings.

The fire that has burned 130 square miles east of Fresno is just one factor that has challenged people planning outdoor activities in recent weeks, officials said Friday.

An infestation of bugs swarmed high-desert communities on the eastern slopes of the Sierra Nevada. In addition, an 18-day manhunt along the famed Pacific Crest Trail ended with the suspect's death.

Katherine Yi of West Los Angeles leads groups of fledgling backpackers each summer in wilderness training classes through the High Sierra, but the large wildfire has forced her to cancel two recent outings.

"It seems like this is becoming the norm," Yi said. "If I try to plan a trip, they have a fire there."

The fire that began on July 31 during a lightning strike has closed roads and about 10 campgrounds around Hume Lake and Kings Canyon. It was 25 percent contained.

U.S. Forest Service spokeswoman Denise Alonzo urged holiday campers to head to the mountains far south of the fire, where they can expect cleaner air and better views of nature, including some of the range's 100 groves of Giant Sequoia trees, some of the Earth's largest and oldest living things.

"We're concerned about people trying to stay in their tents and outdoors with so much smoke in the air," Alonzo said. "It's not healthy."

Smoke from the fire prompted the San Joaquin Valley Air Pollution Control District to issue a health warning to people headed to the mountains and foothills of Tulare and Fresno counties.

The district says children and the elderly are especially vulnerable. Residents on the valley floor from Merced and south to Kern County may also notice smoke into next week.

Half a dozen wildfires were burning throughout California, a relatively small number compared to the past two hot months that kept firefighters running, said Daniel Berlant, a spokesman for the California Department of Forestry and Fire Protection.

Despite the welcomed lull caused by cooler temperatures, he said fire season is entering its peak time.

Vegetation remains dry from the hot summer, and the winds pick up in the transition to fall, fanning the smallest spark.

"Conditions are still just as dry as July and August," he said. "One less spark this Labor Day weekend means one less wildfire."